"interfaces with the environment and is the first line of defense from external factors. For example, the skin plays a key role in protecting the body against pathogens and excessive water loss. Its other functions are insulation, temperature regulation, sensation, and the production of vitamin D folates. Severely damaged skin may heal by forming scar tissue. This is sometimes discoloured and depigmented. The thickness of skin also varies from location to location on an organism. In humans for example, the skin located under the eyes and around the eyelids is the thinnest skin in the body at 0.5 mm thick,"
"skin is the second largest organ in the human body (the inside of the small intestine is 15 to 20 times larger). For the average adult human, the skin has a surface area of between 1.5-2.0 square meters (16.1-21.5 sq ft.). The thickness of the skin varies considerably over all parts of the body, and between men and women and the young and the old. An example is the skin on the forearm which is on average 1.3 mm in the male and 1.26 mm in the female. The average square inch (6.5 cm²) of skin holds 650 sweat glands,"
"lower back can damage the kidneys of the person being hit. The skin of the human back is thicker and has fewer nerve endings than the skin on any other part of the torso. With some notable exceptions (see, e.g. George ""The Animal"" Steele), it tends to have less hair than the chest on men. The upper-middle back is also the one area of the body which a typical human under normal conditions might be unable to physically touch. The skin of the back is innervated by the ""dorsal cutaneous branches"", as well as the ""lateral abdominal cutaneous branches of"
"epidermis itself is only thick. The dermis, the layer underneath the epidermis, is also thin. The hypodermis, containing blubber, is the thickest part of the skin and functions as a means to conserve heat. Right whales have the thickest hypodermis of any cetacean, averaging , though, as in all whales, it is thinner around openings (such as the blowhole) and limbs. Blubber may also be used to store energy during times of fasting. The connective tissue between the hypodermis and muscles allows only limited movement to occur between them. Unlike in toothed whales, baleen whales have small hairs on the"
"organ of the body. In humans, it accounts for about 12 to 15 percent of total body weight and covers 1.5-2m of surface area. The human skin (integument) is composed of at least two major layers of tissue: the epidermis and dermis. (The hypodermis or subcutaneous layer is not part of the skin.) The epidermis is the outermost layer, providing the initial barrier to the external environment. Beneath this, the dermis comprises two sections, the papillary and reticular layers, and contains connective tissues, vessels, glands, follicles, hair roots, sensory nerve endings, and muscular tissue. The deepest layer, the hypodermis, is"
"with the sense of touch. When circulation is severed in a limb, the response to touch and tickle are lost prior to the loss of pain sensation. It might be tempting to speculate that areas of the skin that are the most sensitive to touch would also be the most ticklish, but this does not seem to be the case. While the palm of the hand is far more sensitive to touch, most people find that the soles of their feet are the most ticklish. Other commonly ticklish areas include the underarms, sides of the torso, neck, knee, midriff, perineum,"
"and tend to contribute to the transmission of sexually transmitted diseases in adults. The foreskin is specialized tissue that is packed with nerves and stretch receptors. The foreskin contains Meissner's corpuscles, which are nerve endings involved in fine-touch sensitivity. They are most concentrated in the ""ridged band"", where the inner and outer foreskin layers meet, and least concentrated in the smooth inner layer of foreskin. Compared to other hairless skin areas on the body, the Meissner's index was highest in the finger tip (0.96) and lowest in the foreskin (0.28). The foreskin is the least sensitive hairless tissue of the"
"Human skin The human skin is the outer covering of the body. In humans, it is the largest organ of the integumentary system. The skin has up to seven layers of ectodermal tissue and guards the underlying muscles, bones, ligaments and internal organs. Human skin is similar to most of the other mammals skin, and human skin is very similar to pig skin. Though nearly all human skin is covered with hair follicles, it can appear hairless. There are two general types of skin, hairy and glabrous skin (hairless). The adjective cutaneous literally means ""of the skin"" (from Latin ""cutis"","
"thinner and the epidermis turnover rate for cell repair is lower which may result in the dermis layer being damaged. Skin performs the following functions: The human skin is a rich environment for microbes. Around 1000 species of bacteria from 19 bacterial phyla have been found. Most come from only four phyla: Actinobacteria (51.8%), Firmicutes (24.4%), Proteobacteria (16.5%), and Bacteroidetes (6.3%). Propionibacteria and Staphylococci species were the main species in sebaceous areas. There are three main ecological areas: moist, dry and sebaceous. In moist places on the body Corynebacteria together with Staphylococci dominate. In dry areas, there is a mixture"
"20 blood vessels, 60,000 melanocytes, and more than 1,000 nerve endings. The average human skin cell is about 30 micrometers in diameter, but there are variants. A skin cell usually ranges from 25-40 micrometers (squared), depending on a variety of factors. Skin is composed of three primary layers: the epidermis, the dermis and the hypodermis. Epidermis, ""epi"" coming from the Greek meaning ""over"" or ""upon"", is the outermost layer of the skin. It forms the waterproof, protective wrap over the body's surface which also serves as a barrier to infection and is made up of stratified squamous epithelium with an"
"intermediate layers found in humans are not always distinguishable. Hair is a distinctive feature of mammalian skin, while feathers are (at least among living species) similarly unique to birds. Birds and reptiles have relatively few skin glands, although there may be a few structures for specific purposes, such as pheromone-secreting cells in some reptiles, or the uropygial gland of most birds. Skin performs the following functions: Skin is a soft tissue and exhibits key mechanical behaviors of these tissues. The most pronounced feature is the J-curve stress strain response, in which a region of large strain and minimal stress exists,"
"eight hours to three days. The source of the pressure on the skin can happen from tight fitted clothing, belts, clothing with tough straps, walking, leaning against an object, standing, sitting on a hard surface, etc. The areas of the body most commonly affected are the hands, feet, trunk, abdomen, buttocks, legs and face. Although this appears to be very similar to dermatographism, the cardinal difference is that the swelled skin areas do not become visible quickly and tend to last much longer. This form of the skin disease is, however, rare. Cholinergic urticaria (CU) is one of the physical"
"and is one of the first areas to show signs of aging such as ""crows feet"" and wrinkles. The skin on the palms and the soles of the feet is 4 mm thick and is the thickest skin on the body. The speed and quality of wound healing in skin is promoted by the reception of estrogen. Fur is dense hair. Primarily, fur augments the insulation the skin provides but can also serve as a secondary sexual characteristic or as camouflage. On some animals, the skin is very hard and thick, and can be processed to create leather. Reptiles and"
"Oily skin can be sallow and rough in texture and tends to have large, clearly visible pores everywhere, except around the eyes and neck. Human skin has a low permeability; that is, most foreign substances are unable to penetrate and diffuse through the skin. Skin's outermost layer, the stratum corneum, is an effective barrier to most inorganic nanosized particles. This protects the body from external particles such as toxins by not allowing them to come into contact with internal tissues. However, in some cases it is desirable to allow particles entry to the body through the skin. Potential medical applications"
"is the thickest of the human body, measuring up to 8 mm in thickness, and contains approximately 100.000 hairs. Hair lines make scalp reconstruction difficult because the hair lines must be respected to attain a satisfying aesthetic result. The subCutis is a layer of fat, enclosed in compartments formed by rigid fibrous septa. Their inelasticity prevents bleeding vessels from collapsing and retracting under the skin to achieve haemostasis. All large blood vessels and nerves of the scalp are located in this layer. The next layer is the galea Aponeurotica, which separates the underlying bone and the overlying layers. The large"
"have darker skin pigmentation than their surrounding populations. Dark-skinned humans have high amount of melanin found in their skin. Melanin is derivative of the amino acid tyrosine. Eumelanin is the dominant form of melanin found in human skin. Eumelanin protects tissues and DNA from radiation damage of UV light. Melanin is produced in specialized cells called melanocytes, which are found at the lowest level of the epidermis. Melanin is produced inside small membrane-bound packages called melanosomes. People with naturally occurring dark skin have melanosomes which are clumped, large, and full of eumelanin. A four-fold difference in naturally occurring dark skin"
"skin-like tissue grown in a laboratory, although this technology is still quite a way away from being viable for use in the medical field. 'Artificial skin' can also refer to flexible semiconductor materials that can sense touch for those with prosthetic limbs, (also experimental). The skin is the largest organ in the human body. Skin is made up of three layers, the epidermis, dermis and the fat layer, also called the hypodermis. The epidermis is the outer layer of skin that keeps vital fluids in and harmful bacteria out of the body. The dermis is the inner layer of skin"
"Eccrine sweat gland Eccrine glands (; from ""ekkrinein"" ""secrete""; sometimes called merocrine glands) are the major sweat glands of the human body, found in virtually all skin, with the highest density in palm and soles, then on the head, but much less on the trunk and the extremities. In other mammals, they are relatively sparse, being found mainly on hairless areas such as foot pads. They reach their peak of development in humans, where they may number 200–400/cm² of skin surface. They produce a clear, odorless substance, sweat, consisting primarily of water. Eccrine glands are composed of an intraepidermal spiral"
"the top of the head, underarms and pubic area, the average human has more hair follicles on his or her body than the average chimpanzee. The main distinction is that human hairs are shorter, finer, and less heavily pigmented than the average chimpanzee's, thus making them harder to see. Humans have about 2 million sweat glands spread over their entire bodies, many more than chimpanzees, whose sweat glands are scarce and are mainly located on the palm of the hand and on the soles of the feet. Humans have the largest number of eccrine sweat glands among species. The dental"
"is tightly bound to the underlying tissue and bones. Compared to the rest of the body's skin, the hands' palms (as well as the soles of the feet) are usually lighter — and even much lighter in dark-skinned individuals, compared to the other side of the hand. Indeed, genes specifically expressed in the dermis of palmoplantar skin inhibit melanin production and thus the ability to tan, and promote the thickening of the stratum lucidum and stratum corneum layers of the epidermis. All parts of the skin involved in grasping are covered by papillary ridges (fingerprints) acting as friction pads. In"
"[[dermis]] and the [[hypodermis]]. The epidermis is typically 10 to 30 cells thick; its main function is to provide a waterproof layer. Its outermost cells are constantly lost; its bottommost cells are constantly dividing and pushing upward. The middle layer, the dermis, is 15 to 40 times thicker than the epidermis. The dermis is made up of many components, such as bony structures and blood vessels. The hypodermis is made up of [[adipose tissue]], which stores lipids and provides cushioning and insulation. The thickness of this layer varies widely from species to species; [[marine mammal]]s require a thick hypodermis ([[blubber]])"
"the need so arises. There are two important layers to the human skin: (1) the Epidermis and (2) the Dermis. For transdermal delivery, drugs must pass through the two sublayers of the epidermis to reach the microcirculation of the dermis. The Stratum corneum is the top layer of the skin and varies in thickness from approximately ten to several hundred micrometres, depending on the region of the body. It is composed of layers of dead, flattened keratinocytes surrounded by a lipid matrix, which together act as a brick-and-mortar system that is difficult to penetrate. The stratum corneum provides the most"
"Skin Skin is the soft outer tissue covering of vertebrates. Other animal coverings, such as the arthropod exoskeleton, have different developmental origin, structure and chemical composition. The adjective cutaneous means ""of the skin"" (from Latin ""cutis"", skin). In mammals, the skin is an organ of the integumentary system made up of multiple layers of ectodermal tissue, and guards the underlying muscles, bones, ligaments and internal organs. Skin of a different nature exists in amphibians, reptiles, and birds. All mammals have some hair on their skin, even marine mammals like whales, dolphins, and porpoises which appear to be hairless. The skin"
"therapsids could have had a combination of naked skin, whiskers, and scutes. A full pelage likely did not evolve until the therapsid-mammal transition. The more advanced, smaller therapsids could have had a combination of hair and scutes, a combination still found in some modern mammals, such as rodents and the opossum. In varying degrees most mammals have some skin areas without natural hair. On the human body, glabrous skin is found on the ventral portion of the fingers, palms, soles of feet and lips, which are all parts of the body most closely associated with interacting with the world around"
"mirrored how pheromones affect other mammals. The fingertips have many nerves and are responsive to very light touches, like the brushing of a tongue, light fingernail scratching or teeth stroking. The sides of the fingers are somewhat less sensitive and more ticklish. Both light and firmer touches work well at the junction of the fingers. Human fingertips are the second-most sensitive parts of the body, after the tongue. The thighs can be sensitive to touch. An exaggerated tickle on the back of the legs and knees can also be sensitive for some. Because of the concentration of nerve endings in"
"through the epidermis, glands, or hair follicles. Sweat glands and hair follicles make up about 0.1 to 1.0 percent of the total skin surface. Though small amounts of chemicals may enter the body rapidly through the glands or hair follicles, they are primarily absorbed through the epidermis. Chemicals must pass through the seven cell layers of epidermis before entering the dermis where they can enter the blood stream or lymph and circulate to other areas of the body. Toxins and toxicants can move through the layers by passive diffusion. The stratum corneum is the outermost layer of the epidermis and"
"collagen (collagen VII). DEB-causing mutations can be either autosomal dominant or autosomal recessive. Epidermis bullosa pruriginosa and Albopapuloid epidermolysis bullosa (Pasini's disease) are rare subtypes of this disease. The human skin consists of two layers: an outermost layer called the epidermis and a layer underneath called the dermis. In individuals with healthy skin, there are protein anchors between these two layers that prevent them from moving independently from one another (shearing). In people born with EB, the two skin layers lack the protein anchors that hold them together, resulting in extremely fragile skin—even minor mechanical friction (like rubbing or pressure)"
"in the basal layer of the epidermis. Although, in general, human beings possess a similar concentration of melanocytes in their skin, the melanocytes in some individuals and ethnic groups produce variable amounts of melanin. Some humans have very little or no melanin synthesis in their bodies, a condition known as albinism. Because melanin is an aggregate of smaller component molecules, there are many different types of melanin with different proportions and bonding patterns of these component molecules. Both pheomelanin and eumelanin are found in human skin and hair, but eumelanin is the most abundant melanin in humans, as well as"
"body regions, their numbers remain the same in individual body regions in all human beings. In white and Asian skin the melanosomes are packed in ""aggregates"", but in black skin they are larger and distributed more evenly. The number of melanosomes in the keratinocytes increases with UV radiation exposure, while their distribution remain largely unaffected. Laboratory culture of keratinocytes to form a 3D structure (artificial skin) recapitulating most of the properties of the epidermis is routinely used as a tool for drug development and testing. Epidermis The epidermis is the outermost of the three layers that make up the skin,"
"the point where hairy skin starts. The thin dermis and minimal subcutaneous tissue results in closely set nerve networks. Vater-Pacini corpuscles are present. The mucocutaneous end-organs are formed after birth, with few in newborn infants and many well-organized endings in adults. Cold and Taylor state in 1999 that the foreskin is primary erogenous tissue. Alanis and Lucidi in 2004 describe this as speculative and unproven. Parts of the vulva, especially the clitoris, are erogenous zones. While the vagina is not especially sensitive as a whole, its lower third (the area close to the entrance) has concentrations of the nerve endings"
"the dermis, comprising largely connective tissue, and an outer, thinner epidermis. The thickness of the epidermis ranges from 0.08 mm to greater than 0.6 mm (from 0.003 to 0.024 inches). The epidermis comprises five ""strata""; from outer to inner, they are the stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale. The highest concentrations of 7-dehydrocholesterol are found in the epidermal layer of skin—specifically in the stratum basale and stratum spinosum. The production of pre-vitamin D is, therefore, greatest in these two layers. Synthesis of pre-vitamin D in the skin involves UVB radiation, which effectively penetrates only the"
"Medulla (hair) The medulla is the innermost layer of the hair shaft. This nearly invisible layer is the most soft and fragile, and serves as the pith or marrow of the hair. Scientists are still uncertain about the exact role of the medulla, but they speculate that it is primarily an extension that is more prominent in depigmented (grey or white) hair Human hair is unique in that its medullary index (the fraction of the hair shaft's diameter that the medulla occupies) is very small: generally less than 1/3. Other species will have much larger ratios, usually at least 1/2."
"the epidermis are keratinocytes, melanocytes, Langerhans cells and Merkel cells. The epidermis helps the skin to regulate body temperature. Epidermis is divided into several layers where cells are formed through mitosis at the innermost layers. They move up the strata changing shape and composition as they differentiate and become filled with keratin. They eventually reach the top layer called ""stratum corneum"" and are sloughed off, or desquamated. This process is called ""keratinization"" and takes place within weeks. The outermost layer of the epidermis consists of 25 to 30 layers of dead cells. Epidermis is divided into the following 5 sublayers"